The invention relates to an energy storage and power generation system with at least one fuel cell, in which an oxidant and a fuel which can be stored can be converted electrochemically and in the process an electrical current can be generated, and with at least one electrolysis cell, which is used for generating the fuel which can be stored for the fuel cell, wherein the fuel cell and the electrolysis cell share a common electrode, and the fuel cell and the electrolysis cell each use a respective further electrode only for themselves.
As a result of an increasing proportion of electrical energy from wind or solar energy, the need to buffer-store energy is increased. A possible solution to this is hydrogen which can be generated by electrolysis in an electrolysis cell in the case of a supply of inexpensive and/or regenerative electrical energy which exceeds demand and which can be used for power generation in the case of a supply of inexpensive and/or regenerative electrical energy which falls below the demand, wherein the hydrogen, as a fuel, reacts electrochemically with an oxidant in a fuel cell.
WO2005/008824 has disclosed an electrochemical system with an electrolysis cell and a fuel cell. In this case, in the electrolysis cell, water and a metal are first converted into oxygen and a metal hydride. The metal hydride is converted, by virtue of a change in temperature, into hydrogen and metal and the former is converted back into water by oxygen in the fuel cell. The electrode at which metal is converted into a metal hydride and back again is used jointly by the electrolysis cell and the fuel cell. In this case, the metal hydride acts as the only store for the hydrogen. One disadvantage with this is that only at most as much hydrogen is available for producing electrical power as there is metal available for reaction to form a metal hydride. In order to be able to store a large quantity of hydrogen, a correspondingly large and therefore heavy electrode needs to be provided which increases the weight and costs of the electrochemical system. In addition, the temperature of the fuel cell needs to be selected such that the metal hydride releases hydrogen. In addition, there is the risk of hydrogen embrittlement.